Further evidence in support of the selective uptake and anterograde transport of [¹²⁵I]wheat germ agglutinin by chick retinal ganglion cells

Following intravitreal injection, affinity purified, iodinated wheat germ agglutinin ([¹²⁵I]WGA) is taken up by chick retinal ganglion cells and transported in an anterograde direction to nerve terminals in the optic tectum. The accumulation of axonally transported label in the tectum may be measured quantitatively. Using such an approach, we find that co-injection of [¹²⁵I]WGA with an excess of unlabeled WGA reduces the amount of axonally transported labeled lectin. Since co-injection of comparable levels of soybean agglutinin or Ulex Europeanus-I fails to reduce tectal labeling to a similar extent, and since native WGA at the same concentration does not appear to be toxic to retinal ganglion cells, these results support the hypothesis that the uptake and subsequent anterograde axonal transport of WGA by these cells is a selective process, dependent on a limited number of extra- or intracellular binding sites.